OK, if you’re going to have a shadow, anti-Trump GOP Senate, you need some experienced Republican operatives to staff it. You won’t have to look too hard.
In a clear and public rebuke to Trump, chiefs of staff for Republican presidents Ronald Reagan, George H.W. Bush and George W. Bush recently told the New York Times that the presidents they served would never have asked for help winning an election from a foreign government. A group of conservative lawyers, many of whom served in top positions in the Department of Justice under Reagan or one of the Bushes, are supporting the impeachment inquiry.
Moreover, plenty of people who served in senior roles in the Trump administration itself, including H.R. McMaster (national security adviser), Anthony Scaramucci (communications director) and Rex Tillerson (secretary of state) have distanced themselves from the president.
Again, the Republican staffers currently in the White House are defending the president, but that might mask some broader disagreement among senior-level Republican staffers.